Does Your Lower Back Hurt? Learn Common Causes of Lower Back Pain and Lower Extremity Radiculopathy
Lower back pain can be caused by many different conditions including a herniated disc or sciatica. The Journal of the American Academy of Orthopaedic Surgeons recently published an excellent article on the common causes of lower back pain. This included lower back pain that radiates into the lower extremity. Dr. Bennett Douglas Grimm is the lead author of the Jan 2015 article. A summary of this very informative article is below.
Lower back pain that radiates into the leg is known as lumbar radiculopathy. The prevalence of true lumbar radiculopathy in the general population is approximately 3–5%. The two most common causes for these symptoms are a herniated disc or, less commonly, spinal stenosis.
A lumbar disc herniation most frequently occurs in patients younger than age 50. Symptoms of a herniated disc typically start with severe low back pain that will then radiate into the lower extremity. There may or may not be a traumatic or inciting event that causes the symptoms to start. Initially the low back pain occurs because a tear in the annulus surrounding the disc occurs.
The annulus is richly innervated by nerves which will cause severe pain when torn. After the annulus tears, disc material leaks out and compresses the nerve root going to the lower extremity causing leg pain. It is typically a two-step process. Some people hear or feel a pop at the time of injury which is the annulus tearing.
Once the nerve root is compressed, there may be symptoms of numbness, tingling and weakness involving the lower extremity. Symptoms usually worsen from sneezing or bending forward. Any action that increases intradiscal pressure will cause increased pain such as listed above.
The Physical Exam for Lower Back Pain
An important portion of the physical examination for low back pain is a positive nerve root tension test, also known as a straight leg raise test. This will be present 60% of the time in people who have disc herniation at L4-L5 and L5 and S1. A femoral stretch test may be positive for this condition at L2-3 and L3-4. There may be a decrease in reflexes at the patella tendon or Achilles’ tendon. The patellar tendon represents L4 and the Achilles tendon represents S1.
If there is bowel or bladder dysfunction, or saddle anesthesia is present, there is concern for cauda equina syndrome. This occurs with a very large disc herniation. This is a surgical emergency and requires urgent surgical decompression or permanent nerve damage can occur.
An MRI scan is the best imaging study for the above-mentioned diagnoses.
Spinal Stenosis and Lower Back Pain
Spinal stenosis is another common cause of low back pain and this typically occurs in patients older than 65. Spinal stenosis is caused from osteoarthritis involving the lumbar spine. Typically there is a history of chronic low back pain that radiates into the buttuck and legs.
With spinal stenosis, it is not as common to have only one leg affected, which is typically seen with the disc herniation. Only 20% of the people that present with spinal stenosis would have a positive straight leg raise test. People will complain of pain with ambulation. Their pain will typically stop when they bend forward or sit down. Plain X-rays and an MRI scan are used to help to diagnose this condition.
Additional Causes of Lower Back Pain
There are other causes of lower back pain that occur that have nothing to do with the anatomy of the back but can cause pain in that region of the body. This can be caused from other anatomical structures in the body that are near the low back such as the pelvis and the hip joint.
Conditions such as hip osteoarthritis, osteonecrosis, femoral acetabular impingement, femoral neck stress fractures, pelvic insufficiency fractures, trochanter bursitis of the hip, and sacroiliac joint pain can mimic low back pain. (more…)









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